Mixed Martial Arts is where you get into a ring and you just slug it out. Basically it's like boxing expect in boxing you just box..... whereas in MMA you can box, kickbox, or wrestle. The fighting styles consists of Jiu Jitsu, sambo, kickboxing, wrestling, submission wrestling.... and more styles which I can't think of at this moment. But they aren't just your typical redneck beer drinking brawlers. They are highly trained athletics...many of the fighters actually come from a high school and/or college wrestling backgrounds. They actually train for many months and get paid a nice amount of money for fighting. (the amount that they are paid also depends on their rankings and how popluar/well-known they are among the fans) If you want more information...here are some websites...
www.ufc.tv - (USA based in Las Vegas)
www.pridefc.com - (japan)
www.mmaweekly.com - MMA news
www.maxfighting.com - MMA news
If you have any more questions, don't hesistate to ask!